Surface mount packages for integrated circuit dies typically include input/output connections for electrically coupling the packaged integrated circuit die to external components. One type of conventional package includes input/output (I/O) terminals in the form of peripheral leads extending laterally outward from peripheral edges of the package. Another type of package uses an array of solder balls on the bottom of the package. As technology progresses, integrated circuit dies are being manufactured with an ever increasing number of transistors or monolithic devices performing an ever increasing number of functions, and accordingly require an increasing number of input/output connections.
Peripheral leaded packages, however, are limited in the number of leads or input/output terminals that can be provided by the physical size of the package and the pitch or separation of the leads. For example, a 28 mil..times.28 mil. package with a lead pitch of 0.5 mil typically has 208 leads. In order to increase the number of leads, a larger package can be used or the pitch of the leads can be reduced. For example, a 40 mil..times.40 mil. package with a lead pitch of 0.4 mil. would have 376 leads.
Ball grid (BGA) packages have solder balls arrayed on the bottom of the package. To increase the number of solder balls the package size must be increased and/or the separation of balls or array pitch can be reduced. For example, a 25 mil..times.25 mil. sized package with balls pitched at 60 mil. can have 225 balls, whereas a 40 mil..times.40 mil. package with balls pitched at 50 mil. may have up to 961 balls.
However, it is frequently not desirable, and often impossible, to simply increase the package size or to decrease I/O terminal pitch. For peripheral leaded packages, increasing the package size results in a package that occupies more of the circuit board space, thus increasing costs. Reducing the lead pitch results in a lead of smaller dimensions which is more readily damaged in manufacturing. Additionally, smaller separation between leads is more likely to result in a shorting between leads in a surface mounted arrangement.
In a similar manner, for the ball grid array package a reduction in ball pitch can result in increased yield loss and increased costs of the printed circuit board. The printed circuit board cost increases because the finer pitch requires larger numbers of layers in the printed circuit board for routing connections to the balls, whereas increasing the size of the package increases the area occupied by the package on the printed circuit board, thus increasing the costs.
Accordingly, it is an object of the present invention to provide a surface mounted integrated circuit die package that avoids or minimizes the above mentioned problems.